The present invention generally relates to vehicle wheel alignment techniques and, more particularly, to a wheel alignment system and method for aligning one or more wheels on a vehicle equipped with a steer-by-wire steering system.
Land vehicles are commonly equipped with a set of road wheels that rotate to allow easy movement of the vehicle. Automotive vehicles are conventionally equipped with a pair of front wheels that are controllably steerable to allow the vehicle to turn left and right as it maneuvers on land. Recently, four wheel steering has also become commercially available for use in vehicles. It is important to provide for proper alignment of the wheels such that the wheels roll straight without scuffing, dragging, or slipping under different road conditions. Proper wheel alignment affords sure steering, long tire wear, and places less stress on many vehicle parts. With modern day vehicles, it is common for the front wheels in particular to get out of alignment gradually through normal wear and tear. Accordingly, normal vehicle maintenance may require routine wheel alignments to bring the wheels back into proper alignment.
The conventional wheel alignment technique typically involves a mechanical alignment procedure which requires that the manually operated hand steering wheel be held in a centered position while the vehicle's tie-rods are mechanically loosened and the wheels are individually set to zero degrees. Once the wheels are individually set to zero degrees, such that they are aligned with the body of the vehicle as measured by an alignment fixture, the individual tie-rods are then retightened. The vehicle tie-rods may have to be loosened and retightened repeatedly, depending on the amount of mechanical movement that occurred during the previous tightening processes. The conventional mechanical alignment procedure may require repeated mechanical operations that can result in a time-consuming alignment procedure. The mechanical wheel alignment procedures are further complicated for a four wheel alignment which requires further measurements and adjustments.
Recently, steer-by-wire steering systems have been introduced into automotive vehicles to provide easy to steer wheel control. Included in a typical steer-by-wire steering system is a steering wheel subsystem for monitoring the position of the steering wheel, wheel actuation controllers, and corresponding electric motor actuators for controlling actuation of the individual wheels. The steer-by-wire steering system turns the road wheels left and right with the motor actuators which are controlled by controllers in response to tracking the sensed steering wheel position. In contrast to the presence of a mechanical linkage in prior steering systems, the steer-by-wire steering system does not employ a mechanical linkage between the steering wheel and the individual wheels. For safety and reliability, the steer-by-wire steering system generally employs redundant steering wheel sensors, redundant controllers, and redundant actuators. Similar to other conventional steering systems, the road wheels for a vehicle equipped with the steer-by-wire steering system generally have been aligned according to the time-consuming standard mechanical wheel alignment procedure.
It is therefore one object of the present invention to provide for a quick wheel alignment procedure to align one or more wheels of a vehicle. It is a further object of the present invention to provide for a wheel alignment procedure for quickly and easily aligning one or more wheels of a vehicle equipped with a steer-by-wire steering system. It is yet another object of the present invention to provide for a wheel alignment procedure that efficiently aligns vehicle wheels without requiring readjustment of a mechanical linkage. Yet, it is a further object of the present invention to provide for a vehicle wheel alignment procedure which does not require the vehicle wheels to be initially set to a predetermined direction.